Redox mediators (electron transfer agents) have been employed extensively in electrochemical biosensors used for diagnostic testing of analytes such as glucose, cholesterol, fructose, galactose, nitrate, sulfide, bilirubin and various amino acids. The function of the redox mediator is to shuttle electrons efficiently from the enzymes specific for the analyte (for example, glucose oxidase when glucose is the analyte being measured) to the biosensor's electrode surface. It is a critical component for the successful operation of an electrochemical biosensor. However, many redox mediators used in electrochemical biosensors display notable interference from electroactive species present in samples being measured. Interferents include ascorbic acid, uric acid, acetaminophen and bilirubin. Minimizing interference from these electroactive species presents a formidable challenge in electrochemical biosensor research.